People around the world are welcoming 2016 with fireworks, parties and other festivities, but fears of terrorism mean heightened security in some places or the cancellation of events where large crowds would have gathered to usher in the new year.
Police in Munich, Germany, ordered two train stations evacuated, and service at both locations was stopped. They said there were "indications" that a terror attack was being planned. Authorities also asked the public to avoid large gatherings.
Authorities in Russia closed off Moscow's iconic Red Square, a popular spot for revelers to ring in the new year.
WATCH: Russia Closes Red Square for New Year's Eve
Although not officially acknowledged, the rare move appeared aimed at concerns of terrorism following the October downing of a Russian passenger jet over Egypt and Russia's ongoing bombing campaign in Syria.
Jakarta, Indonesia, was on high alert as police uncovered plans for a terror attack on the capital during festivities.
View the photo gallery of New Year's celebrations around the world:
Authorities in Brussels canceled New Year's Eve fireworks displays amid fears of terrorism. Brussels Mayor Yvan Mayeur said it would have been impossible to adequately screen the thousands of people viewing a fireworks show. He was quoted as saying, "It's better not to take any risks."
Brussels police also said they arrested a 10th suspect in connection with the November terror attacks in Paris that killed 130 people. They reported Thursday that six more people had been detained for questioning about a suspected New Year's Eve terror plot. Two people were arrested earlier in the week in connection with that suspected plan to attack "emblematic" targets in the Belgian capital.
Four of the Islamic extremists linked to the Paris attacks were from Belgium.
Tourists take a selfie in front of a Christmas tree on Brussels' Grand Place, Dec. 31, 2015, after Belgian police held three people for questioning, as part of an investigation into an alleged plot to carry out an attack in the capital on New Year's Eve.
The main fireworks display on Paris' Champs-Elysees avenue was canceled, but authorities said a video would be shown on the Arc de Triomphe. French President Francois Hollande said in a New Year message that France is not finished with terrorism, and that the threat remains at its highest level.
Britain welcomed in 2016 with giant fireworks shows in London and Edinburgh, as hundreds of thousands of revelers hit the streets.
Fireworks filled the clear night sky in London, watched by 113,000 ticket holders lining the banks of the River Thames, along with thousands of others craning for a view from vantage points around the city.
As Big Ben in the Houses of Parliament's clock tower chimed in the New Year, fireworks exploded around the London Eye Ferris wheel on the opposite side of the Thames.
Rio de Janeiro kicked off its Olympic year with a fiesta on Copacabana Beach for more than 2 million people. Brazil's most popular New Year's Eve show was illuminated by 24 tons of fireworks.
To celebrate Rio's hosting of the 2016 Summer Games in August, the soundtrack for revelers included music from previous Olympics and songs paying homage to the samba on its 100th anniversary.
Turkey detains two suspects
Elsewhere, two suspected Islamic State members were detained Wednesday in Turkey. They were believed to be planning suicide attacks on revelers in Ankara.
In downtown Dubai, a massive fireworks display took place as scheduled at midnight local time, even as a massive fire burned at a luxury hotel, leaving at least 14 people injured.
A New York Police Department officer searches a woman as she enters the Times Square, Dec. 31, 2015. Around 1 million people are expected to converge on Times Square for the annual New Year's Eve celebration.
Hours earlier, in Sydney, one of the first places to ring in 2016, Australians were treated to a spectacular fireworks display that lit up the city's famed harbor. The 12-minute light show incorporated seven tons of pyrotechnics that cost $5.1 million.
In Hong Kong, revelers gathered along Victoria Harbor, which was illuminated with a dazzling fireworks display.
In the United States, security will be tight in New York as revelers ring in 2016 with a ball drop above Times Square. Thousands of police, some equipped with rifles or radiation detectors and bomb-sniffing dogs, will be on hand. The celebration is expected to draw more than 1 million people.
Authorities said they were monitoring overseas communications to detect any threats, and they pledged to be vigilant following the recent terror attacks in Paris and in San Bernardino, California.
On Wednesday, authorities in upstate New York arrested a 25-year-old man on charges of planning to attack a restaurant on New Year's Eve in the name of Islamic State. Emanuel Lutchman of Rochester was charged with attempting to provide material support to terrorists.